From my point of view, Diablo 3 is kind of the line in the sand. How much are we really willing to give up?
Starcraft II was sold as an eSports title, with a focus on it's multiplayer. This doesn't excuse the talking abortion that was it's single player component, but that's for a another thread. The OnLine requirement didn't really impact the vast majority of players. It would be like complaining that Counter-Strike requires an internet connection, at least from my point of view.
Diablo, however, has always been a single player game. And Blizzard are attempting to shift the focus entirely to its multiplayer component, however this isn't to the benefit of the game - it's make it's online economy work.
Diablo 3 isn't being built with Co-Op gameplay in mind; 'team work' here is merely 'more damage'. The Hack 'n Slash isn't being changed at a core level to really make deep team work necessary; you jump in, kill mosters, and jump out. No voice chat needed, no plan required.
The only reason the game will feature an 'online only' label is because Blizzard want to ensure your chances of interacting with the online community - and thus drive the Auction House Economy - are as high as they can make it, without making the game an MMO where player interaction on some level is mandatory.
This, to me, is crossing that line in the sand. My gameplay experience is being impacted upon negatively, so that Blizzard can ensure its got a share of the Third Party Item Farmer market.
I won't be buying Diablo 3, because when every game requires an internet connection, when you pay AU$110.00 for a new game and then face an unending cycle of microtransactions, when loading screens are advertisements, forums require subscriptions after the first six months, and 'Gaming' means little more than 'Interactive Advertising and Revenue Streams', I want to be able to say 'I told you so.'
I'll buy Torchlight 2. Blizzard can have it's Item Farmers; I'm out.